Melt spinning process



Mal-d1 31, 1970 TIN Y AM AU MELT SPINNING PROCESS Filed Sent. 29, 1967mvsmox TIN YAH AU ATTORNEY United States Patent 3,504,078 MELT SPINNINGPROCESS Tin Yam Au, Wilmington, Del., assignor to E. I. du Pont deNemours and Company, Wilmington, Del., a corporation of Delaware FiledSept. 29, 1967, Ser. No. 671,832 Int. Cl. D01d /12 U.S. Cl. 264-210 1Claim ABSTRACT OF THE DISCLOSURE This invention provides a high speed,melt-spinning process for producing mixed shrinkage yarn of enhanceddifferential filament length.

Summary of the invention This invention comprises a high speed,melt-spinning process for producing by co-spinning, from a polymer ofPACM containing from 55 to 80% of the trans-trans isomer anddodecanedioic acid and a copolymer of the same composition wherein byweight of said acid is replaced by isophthalic acid, said polymershaving a relative viscosity of 40 to 60, a mixed-shrinkage yarn. Themolten polymers are co-spun at a temperature of at least 300 C. throughseparate holes in a spinneret into a heated non-oxidizing gaseousatmosphere maintained at a temperature of at least 130 C. and thefilaments are withdrawn from the spinneret at a speed of at least 1500y.p.m. such that the tension on the filaments in the spinning andquenching zone is less than 0.20 gram per denier. The filaments arequenched with air and then drawn at least 1.2x. Following draw, thefilaments are annealed without further stretching at a temperature of140 to 190 C.

The resulting yarns exhibit a higher differential shrinkage between thehomopolymer and copolymer filaments after a boil-01f and heat settingtreatment than yarns pro duced under similar conditions but under ahigher spinning tension.

Description of drawings The drawings show a typical set-up for thehigh-speed process of the invention. Homopolymer stream A and copolymerstream B are extruded through separate holes of spinneret C. Chamber Drepresents a diffuser through which steam is passed to blanket thespinneret face. Tail pipe E is a heated conduit that maintains thefilaments at elevated temperatures whereby excessive tension build-up isprevented. The filaments then pass over finish roll F to feed rolls G.The filaments are drawn between feed rolls G and draw rolls H. Someadditional draw may be applied between draw rolls H and annealing rollsI, the latter being enclosed by a heated chamber as indicated by brokenlines. The filaments are then led to a suitable windup means.

Standards and calculations The percent difference in filament length(DFL) between the high and low shrinkage filaments in the mixedshrinkage yarn is determined as follows: A water bath is heated toboiling over a /2 hour period. When the temperature reaches 50 C. askein of the yarn with a suspended weight amounting to 4 mg. per denier(mg.d.) is placed in the bath and remains there for 10 minutes after theboiling point is reached. It is then removed and air dried with theweights attached. The DFL after exposure to heat setting temperature ismeasured by hanging the skein in an oven at 177 C. for 2 minutes under aload of 16 mg.d. A 40-centimeter strand, containing both high and lowshrinkage filaments is cut from the boiled and heat-set skein. Theaverage lengths of the filaments in Patented Mar. 31, 1970 Percent DFL=Wwhere L is the average length of the longer filaments and L is theaverage length of the shorter filaments.

The expression relative viscosity as used herein signifies the ratio ofthe flow time in a viscometer of a polymer solution relative to the flowtime of the solvent by itself. Measurements of relative viscosities asreferred to herein and as measured in the examples is determined from asolution of 3.7 grams of polyamide in 50 ml. of a 1:1 mixture by wt. of98100% formic acid and phenol at 25 C., unless otherwise noted.

EXAMPLE A polymer of bis(4-aminocyclohexyl)methane and dodecanedioicacid (PACM12) containing 70% of the trans-trans isomer and having arelative viscosity of 52 and a copolymer of PACM having the same isomercomposition with by weight of dodecanedioic acid and 10% isophthalicacid having a relative viscosity of 48 are cospun through a singlespinneret containing 36 holes, 18 holes for each polymer. Thesymmetrical Y-shaped spinneret holes consist of three intersectingslots, each of which is 6 mils wide and 15 mils long to producefilaments having a trilobal cross-section. The spinneret blocktemperature (spinning temperature) is 330 C. and the polymer temperaturegoing to the spinneret is 300 C. The spinneret face is surrounded by aradial diffuser through which steam at 235 C. is fed to provide a hotnonoxidizing spinning atmosphere. The steam is further confined belowthe ditfuser by a heated tail pipe about 12 cm. long which is heatedmaintaining a temperature of 235 C. The filaments are then quenched withair, fed to a draw zone by feed rolls at a speed of 1930 y.p.m. in thespinning zone the filaments are under a tension of about 0.12 g.p.d. Thefilaments are then drawn in two stages, 1.175X in each stage, by twopairs of draw rolls operating at 2267 and 2663 y.p.m. respectively. Thesecond pair of draw rolls are heated (thus termed annealing rolls) andenclosed in a heated chest at a temperature of C. The filaments areannealed at substantially constant length on the heated rolls prior tobeing wound up at a speed of 2680 y.p.m.

The drawn yarn is about 60 denier and has a tenacity of 3.40 grams perdenier, an elongation of 33.5%, an initial modulus of 28.0 and anaverage DFL on boil-off and heat-set as described herein of 4.9%.

The tension on the filaments in the spinning zone must be less thanabout 0.2 g.p.d. Highter tensions reduce to an undesirable level theamount of diiferential filament length which can be obtained in the yarnafter boil-off and heat-setting treatment as herein described. The tension may be reduced, for example, by increasing the spinnmg temperature,altering the spinneret orifice dimensions (smaller orifices reduce thetension) and by increasing the temperature of the non-oxidizingatmosphere in the spinning zone. As the spinning speed is increased, thespinning tension increases and adjustments must be made as describedabove to keep the tension below 0.20

mit higher DFL up to a total draw ratio of about 1.4 to 1.7. Draw ratiosof 1.2 to 2.0x are preferred.

Drawn yarn annealing temperatures (temperature of the annealing rolls)of-140 to 190 C. are used. When temperatures less than 140 C. areemployed, it is found that the processed yarn possesses undesirably highshinkage. Above 190 C. the obtainable yarn DFL is substantially reduced.

Spinning tension on the filaments is measured on the quenched filamentsprior to contact with any surfaces such as guide pins or finish rollapplicators. It is measured in a conventional manner using a yarntensiometer such as a Type R-1092 of Rothschild =Instruments,'Zu- 7rich, Switzerland. Since the filaments at the point of measurementcontain no surface lubricant (finish), frictional problems due tofilament contact with the tensiometer can be avoided by spraying alubricant, such as a silicone oil, onto the moving filaments immediatelyprior to contact with the tensiometer measuring surfaces.

What is claimed is:

-1. A high-speed melt-spinning process for producing a mixed shrinkageyarn comprising co-spinning two molten polymer streams, one being ahomopolymer of bis(4- aminocyclohexyl)methane of from 55 to 80%trans-trans isomer and dodecanedioic acid and the other being acopolymerof the same composition wherein about 10% by weight of said acid isreplaced by isophthalic acid, said .4 polymers having a relativelyviscosity of from to 60, at a temperature of at least 300 C, throughseparate holes in a spinneret into a non-oxidizing gaseous atmospheremaintained at a temperature of at least C. and withdrawing the filamentsfrom the spinneret at a speed of at least 1500 yards per minute and at atension less than 0.2 gram per denier, quenching the filaments, drawingthe filaments at least 1.2 and annealing the filaments withoutstretching at a temperature of between C. and C.

References Cited UNITED STATES PATENTS 3,017,686 1/1962 Breen et a1.264l7l X 3,161,914 12/1964 Bloomfield et a1.

3,361,859 1/1968 Cenzato.

3,381,074 4/1968 Bryan et al. 264-l71 3,397,107 8/1968 Kimara et a1.161-173 3,399,108 8/1968 Olson 264171 X 3,418,200 12/1968 Tanner 264171X JULIUS FROME, Primary Examiner J. H. WOO, Assistant Examiner US. Cl.X.R. 264-176, 234

